Novel cotton fiber assemblies of increased absorbency and method

ABSTRACT

Cotton fiber assemblies, such as cotton toweling and diapers, are produced with increased absorbency by fixing cotton fibers in their never-dried botanical growth state and forming the assemblies from the fixed fibers. The never-dried cotton fibers can be fixed with blocking agents such as formaldehyde and acrylamide.

United States Patent [1 1 Ingram et al.

[ 1 Sept. 23, 1975 NOVEL COTTON FIBER ASSEMBLIES OF INCREASED ABSORBENCY AND METHOD lnventorsz Peter Ingram; Brian W. Jones, both of Raleigh; Anton Peterlin, Durham; Joel Lawson Williams, Cary; Donna Kimes Woods, Apex, all of NC.

Assignee: Cotton, Incorporated, New York,

Filed: June 25, 1973 Appl. No.: 372,953

U.S. Cl 8/181; 8/l 16 R; 8/1 16.4; 8/120; S/l25; 252/86; 252/88; 252/89 Int. Cl. D06M 13/34 Field of Search 8/116 R, 181, 116.4, ll5.6, 8/125; 252/875, 8.6, 8.8, 8.9

[56] References Cited UNITED STATES PATENTS 3,177,l43 4/1965 Lense 252/89 3,776,844 l2/l973 Nayfa 252/875 Primary Examiner-Stephen J. Lechert, Jr. Attorney, Agent, or Firm-Burns, Doane, Swecker & Mathis [57] ABSTRACT 12 Claims, 4 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of3 3,907,499

FIXED, NEVER-DRIED FABRIC 2o FIXED,NEVERDR|ED YARN % SORBED 0 CONTROL YARN CONTROL FABRIC (NON-FIXED,0NCE DRIED) I WATER SORPTION ISOTHERMS FDR FIXED,NEVER-DRIED COTTON YARN AND FABRIC (0.25% CH 0) AT 25C.

US Patent Sept. 23,1975 Sheet 2 of 3 3,907,499

o FIXED,NEVERDR|ED FABRIC CONTROL FABRIC (NON-FIXED, H G 2 ONCE-DRIED) DIFFUSION CONSTANTS FOR WATER IN FIXED, NEVER-DRIED FABRICS AT 25 0 I0 2b 3'0 I60 CONC. (g/g H00) FIXED, NEVER-DRIED FABRIC CONTROL FABRIC (NON-FIXED,ONCE DRIED) 9 PERMEABILITY CONSTANTS FOR 5: WATER IN F|XED,NEVER-DRIED FABRIC AT 25C.

I I I P P 0.2 0.4 0.6 0.8 I0

US Patent Sept. 23,1975 Sheet 3 0E3 3,907,499

NON-FIXED NEVER -DRIED FIXED,

NEVER-DRIED NON-FIXED,ONCE DRIED CONTROL d8 E's V2 2.4

t (hrs) He 4 DYE DIFFUSION m FORMALDEHYDE-FIXED NEVER-DRIED COTTON AT 25C NOVEL COTTON FIBER ASSEMBLIES OF INCREASED ABSORBENCY AND METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to cotton fiber assemblies having increased absorbency and to processes for producing the same.

2. Introduction and Summary of the State of the Art Cotton fiber assemblies or products such as towels and diapers have long been in demand due in part to their absorptive properties, and also in part due to their comfort and toughness qualities. Susceptibility to dyeing and other textile modifying treatments such as durable press has also contributed to the popularity of cotton products. The search has continued, however, for cotton fiber assemblies or products having increased absorbency, as well as increased toughness and increased susceptibility to dyeing and other textile modifying treatments. The present invention was made in this search.

Cotton fibers which have been carefully removed from the locks of a boll which has not been allowed to dry out are known to exhibit high internal mobility and be rather porous. For example, they can be stretched further than dried and re-wet fibers before breaking and reversal regions can be observed to spread out in the direction of stretch. Using x-rays, some have concluded generally that cotton in the never-dried botanical growth state is amorphous or at least as having only very low crystallinity, unless it is stretched prior to drying, although an opposite conclusion was reached by others from studying the effect of penetration and ac cessibility or from hydrolysis studies. See, for example, Berkley, E. F. and Kerr, T., Structure and Plasticity of Undried Cotton Fibres, Ind. Eng. (710111., 38, 304 (1946); Berriman, LP, The Role of Growth Rings in Cotton Properties, Text, Res. J., 36, 272 (1966); Usmanov, H. U. Physical Chemistry of Native Cellulose, J. Polymer Sci., 23, 831 (1957); Heyn, A.N.H., Crystalline State of Cellulose in Fresh and Dried Na tivc Cotton Fibers from Unopened Bolls as Studied by X-ray Diffraction, J. Polymer Sci., A3, 1251 (1965); Colvin, J. R., Structure and Biosynthesis of Cellu lose, (RC Critical Revs. in Macrrmwl. Sci 1, 47 (1972); Nelson, M. L. and Mares, T., Accessibility and Lateral Order Distribution of the Cellulose in the Developing Cotton Fibers, Text. Res. .I., 35, 592 (1965); Ono, Y., Studies on the Cotton Fiber as the Material for Cotton Spinning", Part 1. Japan Cotton Textile Institute (1958), Osaka, Japan. Heyn in the above noted article reported the results of his x-ray diffraction studies on cotton fiber samples either dried directly or from which the water has been removed in various indirect ways calculated to better preserve the original structure including: (a) Solvent exchange, (b) freezcdrying, (c) drying above the critical temperature of liquids and (d) drying after the cellulose of the wet fiber has been crosslinked." Greater dyestuff accessibility was disclosed for the solvent exchange (benzenc and pentane) samples. However, no other practi cal considerations which serve to promote the progress of the useful arts were suggested.

SUMMARY OF THE PRESENT INVENTION A major object of the present invention is to provide novel cotton fiber assemblies or products having increased absorbency.

Another object of the present invention is to provide novel cotton fiber assemblies or products having improved toughness (ductility).

Another object of the present invention is to provide novel cotton fiber assemblies or products having improved susceptibility to various textile-modifying treatments.

Another object is to provide processes for producing such novel fiber assemblies or products.

Other objects of the present invention will be apparent to one skilled in the art from the following:

In accordance with the present invention, a cotton fiber assembly having increased absorbency is produced, which assembly comprises cotton fibers fixed or stabilized in their never-dried botanical growth state and formed into a fiber or textile assembly or product.

A major aspect of the present invention is the discovery that assemblies of fixed, never-dried cotton fibers have increased absorbency, as well as improved permeability and diffusion characteristics, as compared with similar fiber assemblies formed from dried-cotton. The fiber assemblies of the present invention can also exhibit improved toughness (ductility or elongation), and improved susceptibility to treatments with textile modifying agents such as creaseproofing agents.

Other aspects and advantages will become apparent to one skilled in the art in view of the following description of the preferred embodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows water sorption isotherms for fabric and yarn made from fixed, never-dried cotton fibers, and for fabric and yarn made from dried cotton fibers;

FIG. 2 shows diffusion constants for water in fabric made from fixed, never-dried cotton fibers, and in fabric made from dried cotton fibers;

FIG. 3 shows permeability constants for water in fabric made from fixed, neverdried cotton fibers, and in fabric made from dried cotton fibers; and

FIG. 4 shows dyeing rates (direct blue) for fixed, never-dried cotton fibers and for dried cotton.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As indicated above, the novel cotton fiber assemblies of the present invention are prepared or produced by a process including fixing the cotton fibers in their never-dried botanical growth state, and then forming the fixed cotton fibers into a fiber assembly.

As used herein, cotton fibers in their never-dried botanical growth state includes those cotton fibers which have been removed from the locks of a cotton boll which has not been allowed to dry out to any significant extent, and which cotton fibers after removal have not been allowed to dry out to any significant extent. In other words, cotton fibers in their never-dried botanical growth state have retained substantially all of their original moisture content.

Never-dried cotton fibers are found to be highly crystalline, and on either drying or stretching inter-fibrillar hydrogen bonding takes place irreversibly. In the case of water sorption behavior, the never-dried cotton typically contains 100% more water than when once dried and re-wet. Also, never-dried cotton fiber typically has at least 50% more extension than cotton fiber once dried and re-wet.

Cotton fibers in their never-dried botanical growth state can typically be obtained by harvesting or otherwise procuring mature cotton bolls just prior to cracking. Prior to fixation, these unopened bolls should be kept completely wet, e.g., submerged in water.

The cotton fibers in their never-dried botanical growth state may be fixed under any conditions which result in the prevention of the irreversible formation of hydrogen bonds between the basic crystalline cellulosic elements composing the fiber, which hydrogen bonding would normally take place during the first fiber drying.

Preferably, the never-dried cotton fibers are fixed by treating the never-dried fibers with at least one blocking agent. The term blocking agent is used herein to define any chemical moiety which when deposited within the never-dried fiber would prevent the irreversible' formation of hydrogen bonding as indicated above. These blocking agents can be further broken down into two classes: (1) permanent blocking agents and (2) temporary blocking agents. Nonlimiting exam ples of these materials are given under their respective headings below:

PERMANENT BLOCKING AGENTS This class of blocking agents would include any compounds which are permanent because of reaction with the cellulose or physical entrapment within the cellulose fiber.

Formaldehyde, acrylamide, and dyes are preferred members of this class.

Other polymerizable compounds may be applicable to this process. Such compounds can either be grafted directly to the cellulose or polymerized in situ to prevent irreversible hydrogen bond formation during the virgin drying of the cotton fiber. Vinyl or vinylidine derivatives can be polymerized in situ or grafted directly to the fiber by a variety of conventional initiator techniques such as peroxides, redox systems, and radiation. Non-limiting examples of such compounds include acrylics (e.g., acrylonitrile, acrylamide, methylacrylate, and ethylacrylate), methacrylics (methylmethacrylate, and ethylmethacrylate), dienes (butadiene, isoprene and chloroprene), and pyridines (2-vinyl pyridine and 4-vinyl pyridine). Condensation type polymers may also be used in a similar fashion as the vinyl or vinylidine derivatives. Non-limiting examples of these compounds include precursors for making polyesters (e.g., polyethylene terephthalate), polyesteramides (e.g., nylon 6,6), polyurethanes, silicones, polyethers, aminoplasts, and furan resins, to name a representative few. Deposition of these materials in fiber systems is per se well known in the textile finishing art.

Another type of blocking or fixing or stabilization of the never-dried cotton state would involve direct reaction with the hydroxyl groups on the cellulose molecules. Both esterification and etherifaction reactions may be applicable. Esterification reactions include carboxylation with acyl halides or anhydrides, phosphorylation (e.g., phosphoric acid and cyanamide), formation of esters of the halogen acid, and organic halides.

Examples of etherification would include reactions with methylolamide and its derivatives, epoxy, cyanuric 4 chloride, and 'vinyl sulfone groups. Such compounds have been used in the textile art and reaction conditions would be apparent to one skilled in the art in view of the present specification.

Dyes may be particularly amenable to the process of the present invention. That is, if the cotton fiber is dyed in the never-dried state the process of dyeing may also become the process of fiber fixation, i.e., the dye not only imparts color to the fiber but the dye itself prevents the normal irreversible hydrogen bond formation which takes place during the drying of the virgin fiber. The different classes of dyes are well known to dye chemists. Examples include anthraquinone derivatives, naphthalene derivatives, and other multi-ring compounds containing functional groups which will either react with thehydroxyl groups in cellulose or form strong secondary bonds.

Other permanent blocking agents may include insoluble inorganic salts and oxides deposited by double decomposition. Organic materials which are insoluble in water but soluble in suitable solvent may be deposited by solvent exchange techniques, e.g., paraffin wax.

TEMPORARY BLOCKING AGENTS Many materials such as water soluble salts or soaps may be used for temporary blockage of the hydroxyl groups. Although temporary blockage is not the preferred aspect of the present invention, it is conceivable that certain textile applications (disposable diapers, for example) might not require the long term stability of more conventional permanent blocking agents. In such cases it might be desirable to use temporary blocking agents, examples of which may include water soluble soaps, salts, and detergents, urea, and starches to name a representative few.

The examples of permanent and temporary blocking or fixation agents given in this embodiment are purely exemplary and other compounds would become apparent to anyone versed in the related art in view of the present specification.

The never-dried cotton fibers are fixed by treating the never-dried fibers with at least one of the abovedescribed blocking agents. Throughout deposition and fixation, the never-dried fibers should be maintained in its never-dried state. For example, the blocking agents may be applied in aqueous solution in which the neverdried fibers are immersed.

It is also preferred but not required that any excess blocking agents or other chemicals following deposition be washed out of the fiber before drying.

Deposition and/or reaction of blocking or fixation agents within the never-dried cotton is typically diffusion controlled, making lower molecular weight blocking agents more favorable in terms of practical treatment times. In this regard, blocking agents with molecular weights ranging from 10 to 100,000 gmw may work. A more preferred range of molecularweights wouldbe from 30 to 2,000 gmw. Optimum conditions of pH for the various types of reaction may be determined by one skilled in the art in view of the present specification. Any pH between 2 and 12 would typically not be detrimental to fiber properites, but a range of pH of between about 3 and 8 may be preferred. Similar considerations apply to fixation reaction time and temperatures. Suitable temperatures may range from between about 0 and 100C, preferably from about 20 to about C.

The amount of blocking or fixation agent deposited may be between about 0.1 and 100% by weight of dry fibrous material, with a preferred range between about 0.1 and It is recognized that the maximum extent of deposition possible for many of the blocking agents may be only a few percent. In such cases an amount near 0.1% by weight may suffice.

Once fixation has been accomplished, cotton fibers are typically washed to remove any excess chemicals and dried and thereafter ginned. One or more ginnings may be used to obtain the desired fiber lengths.

The fixed cotton fibers may then be formed into any fiber assembly, and particularly those fiber assemblies where absorbency is a significant consideration from a use standpoint. Such cotton fibers may be made into yarn and then formed into woven or non-woven or knitted fabrics. Cotton fibers may also be formed into webs or battings for use in disposable diapers and the like. Insofar as the fixed never-dried cotton fiber assemblies of the present invention can absorb 100% more water than normal dried fiber cotton assemblies, typical applications may include drying towels, sweatshirts, diapers, sanitary napkins and blotting paper, to name a representative few; other applications would be apparent to one skilled in the art in view of the present specification. A direct consequence of this" increased absorbency in the fixed never-dried state is the ability of the cotton fiber or fiber assembly to absorb not only more dye than normally dried cotton fiber, but at a higher absorption rate. As a result, deeper and more brilliant shades can be obtained with the same dye with superior uniformity of dyeing.

The fixed never-dried cotton fibers or fiber assemblies are particularly susceptible to treatments with textile modifying agents such as creaseproofing agents (e.g., methylolated 'melamines, dimethyloldihydrox' yethylene urea), soil release agents, dyes, flame retardants,mercerization c'ompounds,'water repellants and fabric softeners. The use of many of these textile modifying agents may exhibit synergistic or improved results when applied to fixed never-dried cotton fibers or fiber assemblies as compared to ordinary dried cotton fiber or dried cotton fiber assemblies.

The present invention is further illustrated by the following examples; all parts and percentages in the examples and throughout the specification are by weight unless otherwise indicated.

EXAMPLE I As unopened (green) boll of cotton that" has been stored in the wet state immersed in distilled water at 4C) was opened under water and a cotton fiber sample of approximately 300 mg was removed. The cotton fiber sample was then fixed in its never-dried botanical growth state using the following fixation solution:

10.2 mls. of an aqueous solution of 37% formaldehyde stabilized with 12 methanol 17.2 mls of an aqueous solution of 38% sulfuric acid 72.6 mls water The never-dried cotton fiber sample was allowed to react for 1 hour at 25C in the above fixation solution. Following fixation the sample was washed three times in distilled water and air dried.

Analysis of the fiber sample treated in the above manner indicated that the cotton contained 0.35% bound formaldehyde. Also, the sample upon re-wetting exhibited long tailing fracture tipsinstead of the normal short fracture tips found with native re-wet cotton. In addition, the elongation at break was 20% for the fixed sample compared to about 10% for normal re-wet cotton, which is alsoindicative of the high internal mobility of the fixed never-dried cotton fiber. Further, higher sorption properties were found as compared to unfixed, dried cotton fibers.

EXAMPLE II A 100 mg sample was removed from an unopened cotton boll as described in Example I. This sample was placed in an aqueous solution containing 500 mg acrylamide and 10 mls of a 5% aqueous solutionof CuCl and bubbled with purified nitrogen for 30 minutes. The sample ampoule was then sealed and irradiated at 25C in a cobalt 60 gamma source to a dose of 0.145 megarads at a dose rate of 0.05 megarads per hour. Following irradiation, the fixed never-dried sample was thoroughly extracted with water and dried.

Analysis of the sample treated in the above manner reveaied that the cotton contained 14% grafted acrylamide. In a similar fashion as in Example I these fibers exhibited 22% elongation at break upon re-wetting compared to about 10% for the normal re-wet dried fiber. Also, the acrylamide fixed fiber had long tailing fracture tips indicative of high internal mobility. In addition, high sorption properties were found for the fixed never-dried cotton fibers following this fixation using acrylamide.

EXAMPLE III Never-dried cotton fibers were removed from unopened bolls under water as described in Example I. The never-dried cotton fibers were placed in an aqueoussolution of acidified formaldehyde for three hours at 25C, and then water rinsed to remove residual chemicals. The fixed never-dried cotton fibers were then air dried.

The same procedure was repeated for the prepara tion of the control fiber with the elimination of the fixation step with formaldehyde.

Both the control and fixed cotton fibers were assembled into fabric form. Before fabric preparation, both samples were ginned to separate the fibers from their seeds. An l8s cotton yarn was then spun from each of the control and fixed cotton fibers for weaving into a fabric construction. The respective samples were carried through yarn formation and then fabricated into a 16 inch width fabric. Before weaving each sample was sized using earboxymethyl cellulose which was removed by washing after weaving.

Several sets of absorption isotherms are plotted in FIG. 1 for the control yarn and fabric and for the fixed never-dried yarn and fabric. Clearly, the fixed materials are seen to absorb more water than the control fabric. The corresponding diffusion and permeability constants for each of the fabrics are given in FIGS. 2 and 3. Here it can be seen that the overall permeability constant is about higher in the case of the fabric made from fixed never-dried fibers.

Other properties for the control dried cotton fibers and the fixed never-dried cotton fibers (0.25% bound formaldehyde content) used in the preparation of the fabrics are shown in the following table.

Test (at 20C, 65% RH) Control Fixed, Never-Dried Micronaire 3.52 3.35

2.5% Span 1.188 1.140

7: Uniformity 46.7 42.0

7: Short Fiber 4.33 1 1.77 Pressley gauge psi 83,590 73,120 Gram/tex Vs gauge 24.98 I 21.07

74- Elongation 5.25 6.00

71 Nonlint 13.50 12.9

As may be seen from the above, the transport (water) properties of fixed never-dried cotton fiber,- yarn and fabric show that improved sorptive properties are obtained with respect to control fibers, fabrics and yarn of ordinary dried cotton fiber.

EXAMPLE 1V Dye runs were carried out using a blue direct dye (Amanil Skyblue FF) on the never-dried cotton fibers, the fixed never-dried cotton fibers and the control, once dried fibers discussed in Example 111. Results are summarized in FIG. 4 which shows the dyeing rates for fixed, never-dried cotton fibers and for once dried cot ton fibers. As may be seen from FIG. 4, the dyeing rates for the never-dried and fixed never-dried samples are approximately the same. The actual increase in dyeing rate over the control dried cotton fibers is about 37%.

Similar runs using a red reactive dye (Procion Red MXSB) indicate that high levels of dyeing take place on never-dried cotton fibers with this class of dyes. Dyeing with reactive dyes may also serve to fix the never-dried cotton fibers in their botanical growth state.

The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. However, it should be understood that the invention which is intended to be protected herein may be practiced otherwise than as described without departing from the scope of the appended claims.

We claim:

1. A process for producing a cotton fiber assembly having increased absorbency, which process comprises A. stabilizing cotton fibers in their never-dried botanical growth state by treating the never-dried fibers with at least one blocking agent and B. forming the stabilized cotton fibers into a fiber assembly.

2. A process according to claim 1 wherein the blocking agent is reacted with the cotton fibers.

3. A process according to claim 2 wherein the blocking agent is acrylamide.

4. A process according to claim 1 wherein the blocking agent is selected from the group consisting of formaldehyde, acrylamide, and dyes.

5. A process according to claim 1 wherein formation of the fiber assembly includes forming yarn from the fixed cotton fibers, and weaving fabric from the yarn.

6. A process according to claim 1 wherein the fiber assembly is subsequently treated with at least one textile-modifying agent.

7. A process according to claim 6 wherein the textile modifying agent isselected from the group consisting of creaseproofing agents, soil-release agents, dyes, flame retardants, mercerization compounds, waterrepellants and fabric softeners.

8. A cotton fiber assembly having increased absorbency, which assembly comprises cotton fibers stabilized in their never-dried botanical growth state by having at least one blocking agent deposited therewithin and formed into an assembly.

9. A cotton assembly according to claim 8 wherein the blocking agent is acrylamide.

10. A cotton fiber assembly according to claim 9 wherein the blocking agent is selected from the group consisting of formaldehyde, acrylamide, and dyes.

11. A cotton fiber assembly according to claim 9 wherein the fiber assembly is a fabric woven from yarns of fixed cotton fibers.

12. A cotton fiber assembly according to claim 9 and treated with at least one textile-modifying agent selected from the group consisting of creaseproofing agents, soil-release agents, dyes, flame retardants, mercerization compounds, water-repellants and fabric softeners. 

1. A PROCESS FOR PRODUCING A COTTON FIBER ASSEMBLY HAVING INCREASED ABSORBENCY, WHICH PROCESS COMPRISES A. STABLING COTTON FIBRES IN THEIR NEVER-DRIED BOTANCIAL GROWTH STATE BY TREATING THE NEVER-DRIED FIBRES WITH AT LEAST ONE BLOCKING AGENT AND B. FORMING THE STABILIZED COTTON FIBRES INTO A FIBRE ASSEMBLY.
 2. A process according to claim 1 wherein the blocking agent is reacted with the cotton fibers.
 3. A process according to claim 2 wherein the blocking agent is acrylamide.
 4. A process according to claim 1 wherein the blocking agent is selected from the group consisting of formaldehyde, acrylamide, and dyes.
 5. A process according to claim 1 wherein formation of the fiber assembly includes forming yarn from the fixed cotton fibers, and weaving fabric from the yarn.
 6. A process according to claim 1 wherein the fiber assembly is subsequently treated with at least one Textile-modifying agent.
 7. A process according to claim 6 wherein the textile modifying agent is selected from the group consisting of creaseproofing agents, soil-release agents, dyes, flame retardants, mercerization compounds, water-repellants and fabric softeners.
 8. A cotton fiber assembly having increased absorbency, which assembly comprises cotton fibers stabilized in their never-dried botanical growth state by having at least one blocking agent deposited therewithin and formed into an assembly.
 9. A cotton assembly according to claim 8 wherein the blocking agent is acrylamide.
 10. A cotton fiber assembly according to claim 9 wherein the blocking agent is selected from the group consisting of formaldehyde, acrylamide, and dyes.
 11. A cotton fiber assembly according to claim 9 wherein the fiber assembly is a fabric woven from yarns of fixed cotton fibers.
 12. A cotton fiber assembly according to claim 9 and treated with at least one textile-modifying agent selected from the group consisting of creaseproofing agents, soil-release agents, dyes, flame retardants, mercerization compounds, water-repellants and fabric softeners. 